Biocidal compositions and treatments

ABSTRACT

A synergistic biocide comprises a tris(hydroxymethyl)phosphine or a tetrakis (hydroxymethyl)phosphonium salt and at least one non-surfactant biopenetrant, such as a polymer or copolymer having a plurality of quaternary ammonium groups, a hydrotrope or a syntan, together optionally with a surfactant.

The present invention relates to synergistic biocidal mixtures ofhydroxymethyl phosphonium biocides with certain non-foamingbiopenetrants.

GB 2 145 708 describes biocidal uses of tetrakis (hydroxymethyl)phosphonium salts. which, together with their parent base,tris(hydroxymethyl)phosphine, are referred to herein collectively as“THP”. U.S. Pat. No. 4,778,813 describes the biocidal use of quaternaryammonium polymers. GB 2 178 960 describes synergism between THP andsurfactant. GB 2 228 680 describes synergism between THP and certainaldehydes.

THP formulations are increasingly widely used as biocides for watertreatment in treating cooling water, process water e.g. in pulp andpaper manufacture, drilling fluids and other aerobic water systems, aswell as in anaerobic systems such as oil field formation water,injection water, produced water and water used in hydrostatic testing.Advantages include rapid and effective bactericidal activity andenvironmental acceptability. Particularly in systems where slime formingbacteria proliferate (e.g. in aerobic systems such as cooling water) ithas been found desirable to use THP formulations containing synergisticamounts of a surfactant according to GB 2 178 960, in order to improvecost effective biocidal action. It is believed that the surfactant aidsthe penetration of the biomass by the THP. However such formulationscause foaming problems. Attempts to combine THP with other biocides(e.g. aldehydes), which do not cause foaming, have not been able toprovide such effective biocidal action against slime forming bacteria,and/or have detracted from the favourable environmental profile of THP.

We have now discovered that combinations of THP with certainnon-surfactant biopenetrants provide strongly synergistic biocidalformulations which give excellent penetration of bacterial slime andimproved activity against planktonic bacteria without causing excessivefoam. We have further discovered that mixtures of THP with a surfactant,and with a non-surfactant biopenetrant give a marked ternary synergism,permitting improved biocidal efficiency with reduced foaming.

Our invention provides a biocidally synergistic mixture comprising THPand at least one THP-compatible, non-surfactant, biopenetrant synergisttogether optionally with a surfactant The non-surfactant biopenetrantmay be selected from quaternary ammonium polymers and copolymers,hydrotropes and syntans.

According to a second embodiment the invention provides a method oftreating aqueous systems contaminated, or liable to contamination, withmicrobes such as bacteria. fungi or algae which comprises applyingthereto separately or together a biocidally active amount of thecomponents of a synergistic mixture as aforesaid.

The aqueous system may, for instance, be contaminated with bacterialslime and/or planktonic bacteria. The invention is of use for treatingaerobic systems such as cooling towers and also for anaerobic systems,such as oil wells, e.g. during secondary recovery.

The THP is conveniently present in the formulation as a salt, but ispreferably used at a pH sufficient to form the base. The salt ispreferably the sulphate, chloride or phosphate. However any watersoluble salt may be used including the phosphite, bromide, fluoride,carbonate, acetate, formate, citrate, borate, or silicate In fact anycounter ion which is chemically compatible with THP may be used, themain criteria for selection being economic. Oxidation of THP totris(hydroxymethyl)phosphine oxide (THPO) should be avoided andoxidising agents for THP are preferably substantially absent. Thecomposition may contain oxygen scavengers to minimise oxidation byatmospheric oxygen. The pH of the composition may be below 3.5 to avoidTHPO formation during storage but the pH on addition to aqueous systemsis preferably between 3.5 and 9 and more preferably less than 8, e.g. 4to 7.5. High alkalinity, e.g. above 10, is preferably avoided. The pH ofthe aqueous system may optionally be adjusted by addition of alkali oracid as appropriate.

An essential component of the invention is a non-surfactantbiopenetrant. Surfactants are amphiphilic compounds which, even whenpresent in low concentrations in water (e.g. 0.1% by weight),substantially reduce the interfacial free energy of a water/hydrophobeinterface. Surfactants may be identified by their effect on surfacetension of water. Non-surfactants do not appreciably reduce surfacetension at low concentrations. Typically the reduction of surfacetension by a non-surfactant at concentrations of the order of 0.1% doesnot amount to more than about 5% of the value for pure distilled water.At the same concentrations typical surfactants would reduce surfacetension by 50% or more. For the purposes of this specification acompound is considered non-surfactant if it lowers the surface tensionof water by less than 20% at a concentration of 0.1% by weight.Preferably the reduction is less than 15%, e.g. less than 10%,especially less than 5%.

The non-surfactant biopenetrant may for example be a quaternary ammoniumpolymer or copolymer. The quaternary ammonium polymer may for example beany of those described in U.S. Pat. No. 4,778,813. Particularlypreferred is poly[oxyethylene(dimethyliminio)ethylene(dimethyliminio)ethylene dichloride]. This a copolymer ofNNN′N′-tetramethyl-1,2-diamino ethane with bis (2-chloroethyl) ether,which is referred to herein as “WSCP”. The latter is the commercial nameof the product used in example 1, which is sold by Buckman Laboratories.However any other water soluble polymer containing a plurality ofquaternary ammonium groups may be used. Such compounds typicallycomprise a polymeric cation of the formula:

wherein: each R is a divalent organic group constituting with theammonium group a monomeric residue or separately selected from two ormore comonomeric residues; each R¹ is an alkyl or hydroxy alkyl group,typically having from 1 to 4 carbon atoms and preferably methyl orethyl; X is hydrogen or a monovalant inorganic or organic end cappinggroup; and n is from 2 to 3000, e.g. 5 to 2000, especially 8 to 1000,e.g. 10 to 500, most preferably 20 to 100. The counter ion may be anyconvenient THP-compatible anion e.g. chloride, sulphate, phosphate,bromide, fluoride, carbonate, formate, acetate, citrate, lactate,tartrate, methosulphate, borate or silicate.

R may for example be a C₁₋₆ alkylene, oxyalkylene, polyoxyalkylene,haloalkylene, halooxyalkylene, halopolyoxyakylene or a

group wherein R² may be a C₁₋₆ alkylene, oxyalkylene polyoxyalkylene,haloalkylene, halooxyalkylene or halopolyoxyalkylene group and R³represents a covalent bond or an R² group. The polymer may for examplebe a methylated polyethylene polyamine of the formula

where n is 2 to 10.

Some other typical examples include:

Poly[hydroxyethylene(dimethyliminio)ethylene(dimethyliminio)methylenedichloride]

Poly[hydroxyethylene(dimethyliminio)-2-hydroxypropylene(dimethyliminio)-methylenedichloride]

N-[3-(dimethylammonio)propyl]-N[3-(ethyleneoxyethylenedimethylammonio)propyl]urea dichloride

-4-[1-tris(2-hydroxyethyl)ammoniumchloride-2-butenyl]poly[1-dimethyl-ammoniumchloride-2-butenyl]tris(2-hydroxyethyl)ammonium chloride

The non-surfactant biopenetrant may alternatively be a hydrotrope.Hydrotropes are sometimes confused with surfactants because they arealso amphiphilic. However hydrotropes do not significantly affectsurface tension at low concentrations. Hydrotropes act as solubilisers.When present in relatively high concentrations (e.g. greater than about1%) they increase the water solubility of sparingly or moderatelysoluble solutes.

A preferred class of hydrotropes includes water soluble glycol ethers.The glycol ether is preferably a water soluble compound of the formulaHO[CR₂CR₂O])_(n)R′ where each R is methyl, ethyl or preferably H,provided that the total number of carbon atoms per [CR₂CR₂O] group doesnot exceed 4, more preferably is not more than 3 and most preferably is2, R′ is a lower hydrocarbon group such that the compound is watersoluble, e.g. butyl, propyl, ethyl or preferably methyl and n is from 1to 20, preferably 1 to 10, especially 1 to 5, typically 1 to 3, mostpreferably 2. Preferred examples include diethylene glycol monomethylether.

An important class of hydrotropes for use according to our inventioncomprises the lower alkyl aryl sulphonates. Water soluble salts, e.g.sodium, potassium, ammonium or salts of benzene sulphonic, toluenesulphonic, xylene sulphonic, ethyl benzene sulphonic or cumene sulphonicacids are very effective. Generally, alkylbenzene sulphonic acids havingup to four or even five aliphatic carbon atoms show hydrotropicity butnot significant surfactancy. Above six aliphatic carbons, e.g. sodiumoctyl benzene sulphonate, surfactancy predominates over hydrotropicity.Naphthalene sulphonates are also useful as non-surfactant biopenetrants,e.g. alkali metal C₁₋₄ alkyl naphthalene sulphonates. Urea is also aneffective hydrotrope.

A further category of non-surfactant biopenetrants comprises syntans.The latter include a variety of resins and prepolymers which are used inthe tanning industry as an alternative to tannin or chrome.

Animal skins comprise a layer of collagen, and tanning agents react tocross link reactive sites within the collagen. One effect of thisreaction is to increase the minimum temperature at which the leathertends to shrink in hot water.

For the purpose of this specification “syntan” is used to refer tosynthetic organic compounds capable of reacting with collagen to formcross links so as to increase the shrink temperature of leather. Forexample the term includes any water soluble polymer prepared bycopolymerising formaldehyde, which is capable of increasing the shrinkresistance of collagen and which comprises at least two units of theformula

where each M is an aryl group such as a phenyl, naphthyl or anilinegroup substituted with one or more hydroxyl and/or sulphate, sulphone orsulphonimide groups or a nitrogenous comonomer such as a dicyandiamide,urea or melamine residue. As used herein the term “syntan” also includesresin syntans which are homopolyrners and copolymers of unsaturatedcarboxylic acids or their salts. esters, amides or nitrites, e.g.acrylic acid, methacrylic acid, acrylamide, acrylonitrile, maleic acid,fumaric acid, itaconic acid, aconitic acid, crotonic acid, isocrotonicacid, citraconic acid, mesaconic acid, angelic acid, tiglic acid andcinnamic acid. The copolymers may also comprise other vinylic comonomerssuch as styrene. Also included are acetone condensates with, for examplesulphones and sulphonamides, and dicyandiamide based resins.Particularly preferred are: sulphonated aryl formaldehyde copolymers;condensates of THP with nitrogen compounds; phosphono polyacrylate ormaleate telomers such as those described in EP 0 491 391; or phosphonoethyl phosphino telomers as described in EP 0 861 846.

The sulphonated aryl formaldehyde copolymer may for example be sodiumnaphthalene sulphonate formaldehyde condensate, sodium phenolformaldehyde concentrate, or sodium resorcinol formaldehyde condensate,or a condensate of formaldehyde with a sodium alkyl benzene ornaphthalene sulphonate having less than 5 carbon atoms.

THP condensates may contain 2 or more phosphorus atoms, so long as thephosphorus compound is water soluble to a concentration of at least 0.5g/l at 25° C. Such phosphorus compounds contain a total of at least 2hydroxymethyl groups, usually at least one per phosphorus atom, andpreferably at least 2 hydroxymethyl groups per phosphorus atom. Thegroup or groups joining the phosphorus atoms together may be of theformula —R—, —R—O—, —R—O—R—, —R—NH—R or —R—R″—R— where R is an alkylenegroup of 1 to 4 carbon atoms and R″ is the residue formed by removal oftwo hydrogen atoms, bonded to nitrogen, from a di or polyamide or anamine or di or polyamine, such as urea, a C₁₋₂₀alkylamine,dicyandiamide, thiourea or guanidine. Such compounds with 2 or more,e.g. 3, hydroxyalkyl groups per phosphorus atom may be made by selfcondensation of THP salts with a compound of general formula R″H₂ suchas urea, or a C_(1 to 20)alkylamine, e.g. by heating at 40 to 120° C.

The THP condensate may be prepared in situ by adding THP and a minorproportion of (for example) a condensable comonomer such as urea,melamine, an amine or dicyandiamide, simultaneously or consecutively tothe system to be treated. Thus, for example, urea or aryl sulphonatehydrotrope may function as hydrotropes or comonomers for the in situformation of syntans or in both capacities, in accordance with ourinvention.

The phosphono telomer may be a compound of the formula

H[CHRCHR]_(n)—PO₃M₂

wherein at least one R group in each unit is a COOM, CH₂OH, sulphono orphosphono group and the other r group which may be the same as, ordifferent from, the first R group, is hydrogen or a COOM, hydroxyl,phosphono, sulphono, sulphate and/or hydroxy substituted C₁₋₇ alkyl orC₁₋₇ alkenyl group, and each M is a cation such that the phosphonatedoligomer is water soluble and n is greater than 1, e.g. up to 10.

It is possible to use cotelomers, e.g. of the above formula, but inwhich the [CHRCHR]n chain contains at least two [CHRCHR] groups derivedfrom different monomers and in which n has a total value of at least 3.For example we include a phosphonated trimer or higher cooligomer ofmaleate and acrylate containing at least one [CH₂ CHCOOM] and at leastone [CHCOOM CHCOOM] group.

Particularly preferred are phosphonated oligomers of maleic acid, of theformula H(CHCO₂M.CHCO₂M)_(a)PO₃M₂ where n is greater than 1 and M is acationic species such that the compound is water soluble, and especiallymixtures of such compounds with phosphonosuccinic acid or its watersoluble salts.

Particularly preferred are mixtures of phosphonosuccinate salts and anoligomer of the above formula when n=2, such as may be prepared byreacting sodium phosphite with a small molar excess of sodium maleate ina concentrated alkaline aqueous solution at elevated temperatures in thepresence of a free radical source such as hydrogen peroxide.

Other phosphono telomers which are used according to the inventioninclude phosphono acrylate telomers, e.g. of the formula:

M₂O₃P[CH₂CHCOOM]_(n)H

where n may be 2 to 60, preferably 3 to 30, e.g. 4 to 20.

1-Phosphono-2-phosphino ethane can be reacted with salts oftelomerisable unsaturated acids such as maleic and acrylic to makesyntans which are useful in the present invention. Other phosphonocarboxylates of use include phosphonosuccinates and salts of2-phosphono-1,2,4-tricarboxy butane.

The biopenetrant synergist is not usually present in a greater weightconcentration than the THP, although higher concentrations by weightbased on THP, e.g. up to 10:1 or even 100:1 are technically possible butcommercially undesirable. The proportion is preferably less than 50% byweight based on the weight of THP, more usually less than 20%, typicallyless than 10%, especially less than 5%. Although very small amounts maybe effective we prefer to use proportions of biopenetrant greater than0.1% based on the weight of THP, usually greater than 0.5%, especiallygreater than 1%.

The biocide is typically supplied as a 10 to 75%, e.g. 20 to 60%,especially 30 to 50% by weight aqueous solution of THP containing from0.1 to 10% e.g. 0.2 to 5%, especially 0.5 to 2% of the synergist, basedon the total weight of the solution.

Alternatively the composition may be supplied as a solid formed bycoating THP onto, or absorbing it into, a powdery granular or porousacid substrate such as adipic acid.

The mixture is typically used at a dosage of 1 to 1500 ppm by weight THPbased on the weight of water to be treated, usually 2 to 500, especially5 to 250, e.g. 10 to 150.

According to a particular embodiment it has been found that mixtures ofthe aforesaid biopenetrant synergists with surfactants and THP saltsprovide an enhanced synergism. Such mixtures can provide even moreeffective biocidal activity, at substantially lower levels of bothbiocide and surfactant than arm required for conventional mixtures ofTHP salts and surfactant.

Our invention accordingly further provides a biocidally synergisticmixture comprising: (A) THP; (B) at )cast one non-surfactantbiopenetrant; and (C) a surfactant.

The invention further provides a method of treating water with abiocidally active amount of said synergistic mixture.

Surfactants for use in our invention typically contain hydrophobicgroups such as alkenyl, cycloalkenyl, alkyl, cycloalkyl, aryl,alkyl/aryl or more complex aryl (as in petroleum sulphonates) moietieshaving from 8 to 22, preferably 10 to 20, typically 12 to 18 carbonatoms and a hydrophilic moiety. Other hydrophobic groups included in theinvention are polysiloxane groups.

The surfactant may for example consist substantially of an at leastsparingly water-soluble salt of sulphonic or mono esterified sulphuricacids, e.g. an alkylbenzene sulphonate, alkyl sulphate, alkyl ethersulphate, olefin sulphonate, alkane sulphonate, alkylphenol sulphate,alkylphenol ether sulphate, alkylethanolamide sulphate,alkylethanolamidether sulphate, or alpha sulpho fatty acid or its estereach having at least one alkyl or alkenyl group with from 8 to 22, moreusually 10 to 20, aliphatic carbons atoms.

The expression “ether” hereinbefore refers to compounds containing oneor more glyceryl groups and/or an oxyalkylene or polyoxyalkylene groupespecially a group containing from 1 to 20 oxyethylene and/oroxypropylene groups. One or more oxybutylene groups may additionally oralternatively be present. For example, the sulphonated or sulphatedsurfactant may be sodium dodecyl benzene sulphonate, potassium hexadecylbenzene sulphonate, sodium dodecyl dimethyl benzene sulphonate, sodiumlauryl sulphate, sodium tallow sulphate, potassium oleyl sulphate,ammonium lauryl monoethoxy sulphate, or monoethanolamine cetyl 10 moleethoxylate sulphate.

Other anionic surfactants useful according to the present inventioninclude alkyl sulphosuccinates, such as sodiumdi-2-ethylhexylsulphosuccinate and sodium dihexylsulphosuccinate, alkylether sulphosuccinates, alkyl sulphosuccinamates, alkyl ethersulphosuccinomates, acyl sarcosinates, acyl taurides, isethionates,soaps such as stearates, palmitates, resinates, oleates, linoleates, andalkyl ether carboxylates. Anionic phosphate esters and alkylphosphonates, alkyl amino and imino methylene phosphonates may also beused. In each case the anionic surfactant typically contains at leastone aliphatic hydrocarbon chain having from 8 to 22, preferably 10 to 20carbon atoms, and, in the case of ethers, one or more glyceryl and/orfrom 1 to 20 oxyethylene and/or oxypropylene and/or oxybutylene groups.

Preferred anionic surfactants are sodium salts. Other salts ofcommercial interest include those of potassium, lithium, calcium,magnesium, ammonium, monoethanolamine, diethanolamine, triethanolamine,alkyl amines containing up to seven aliphatic carbon atoms, and alkyland/or hydroxyalkyl phosphonium.

The surfactant may optionally contain or consist of nonionicsurfactants. The nonionic surfactant may be, e.g. a C₁₀₋₂₂ alkanolamideof a mono or di- lower alkanolamine, such a coconut monoethanolamide.Other nonionic surfactants which may optionally be present, includetertiary acetylenic glycols, polyethoxylated alcohols, polyethoxylatedmercaptans, polyethoxylated carboxylic acids, polyethoxylated amines,polyethoxylated alkylolamides, polyethoxylated alkylphenols,polyethoxylated glyceryl esters, polyethoxylated sorbitan esters,polyethoxylated phosphate esters, and the propoxylated or ethoxylatedand propoxylated analogues of all the aforesaid ethoxylated nonionics,all having a C₈₋₂₂ alkyl or alkenyl group and up to 20 ethyleneoxyand/or propyleneoxy groups. Also included arepolyoxypropylene/polyethylene oxide copolymers,polyoxybutylenelpolyoxyethylene copolymers andpolyoxybutylene/polyoxypropylene copolymers. The polyethoxy,polyoxypropylene and polyoxybutylene compounds may be endcapped with,e.g. benzyl groups to reduce the foaming tendency.

Compositions of our invention may contain amphoteric surfactant.

The amphoteric surfactant may for example be a betaine, e.g. a betaineof the formula: R₃N⁺CH₂COO⁻, wherein each R is an alkyl, cycloalkyl,alkenyl or alkaryl group and preferably at least one, and mostpreferably not more than one R, has an average of from 8 to 20, e.g. 10to 18 aliphatic carbon atoms and each other R has an average of from 1to 4 carbon atoms. Particularly preferred are the quaternary imidazolinebetaines of the formula:

wherein R and R′ are alkyl, alkenyl, cycloalkyl, alkaryl or alkanolgroups having an average of from 1 to 20 aliphatic carbon atoms and Rpreferably has an average of from 8 to 20, e.g. 10 to 18 aliphaticcarbon atoms and R′ preferably has 1 to 4 carbon atoms. Other amphotericsurfactants for use according to our invention include alkyl amine ethersulphates, sulphobetaines and other quaternary amine or quaternisedimidazoline sulphonic acids and their salts, and Zwitterionicsurfactants, e.g. N-alkyl taurines, carboxylated amido amines such asRCONH(CH₂)₂N⁺ (CH₂CH₂CH₃)₂CH₂CO⁻ ₂, and amino acids having, in eachcase, hydrocarbon groups capable of conferring surfactant properties(e.g. alkyl, cycloalkyl alkenyl or alkaryl groups having from 8 to 20aliphatic carbon atoms). Typical examples include 2-tallow alkyl,1-tallow amido alkyl, 1-carboxymethyl imidazoline and 2 coconut alkylN-carboxymethyl 2 (hydroxyalkyl) imidazoline. Generally speaking anywater soluble amphoteric or Zwitterionic surfactant compound whichcomprises a hydrophobic portion including C₈₋₂₀ alkyl or alkenyl groupand a hydrophilic portion containing an amine or quaternary ammoniumgroup and a carboxylate, sulphate or sulphonic acid group may be used inour invention.

Compositions of our invention may also include cationic surfactants.

The cationic surfactant may for example be an alkylammonium salt havinga total of at least 8, usually 10 to 30, e.g. 12 to 24 aliphatic carbonatoms, especially a tri or tetra-alkylammonium salt. Typicallyalkylammonium surfactants for use according to our invention have one orat most two relatively long aliphatic chains per molecule (e.g. chainshaving an average of 8 to 20 carbon atoms each, usually 12 to 18 carbonatoms) and two or three relatively short chain alkyl groups having 1 to4 carbon atoms each, e.g. methyl or ethyl groups, preferably methylgroups. Typical examples include dodecyl trimethyl ammonium salts.Benzalkonium salts having one 8 to 20 C alkyl group two 1 to 4 carbonalkyl groups and a benzyl group are also useful.

Another class of cationic surfactant useful according to our inventioncomprises N-alkyl pyridinium salts wherein the alkyl group has anaverage of from 8 to 22, preferably 10 to 20 carbon atoms. Othersimilarly alkylated heterocyclic salts, such as N-alkyl isoquinoliniumsalts, may also be used.

Alkylaryl dialkylammonium salts, having an average of from 10 to 30aliphatic carbon atoms are useful, e.g. those in which the alkylarylgroup is an alkyl benzene group having an average of from 8 to 22,preferably 10 to 20 carbon atoms and the other two alkyl groups usuallyhave from 1 to 4 carbon atoms, e.g. methyl groups.

Other classes of cationic surfactant which are of use in our inventioninclude alkyl imidazoline or quaternised imidazoline salts having atleast one alkyl group in the molecule with an average of from 8 to 22preferably 10 to 20 carbon atoms. Typical examples include alkyl methylhydroxyethyl imidazolinium salts, alkyl benzyl hydroxyethylimidazolinium salts, and 2 alkyl-1-alkylamidoethyl imidazoline salts.

Another class of cationic surfactant for use according to our inventioncomprises the amido amines such as those formed by reacting a fatty acidhaving 2 to 22 carbon atoms or an ester, glyceride or similar amideforming derivative thereof, with a di or poly amine, such as, forexample, ethylene diamine or diethylene triamine, in such a proportionas to leave at least one free amine group. Quaternised amido amines maysimilarly be employed.

Alkyl phosphonium and hydroxyalkyl phosphonium salts having one C₈₋₂₀alkyl group and three C₁₋₄ alkyl or hydroxyalkyl groups may also be usedas cationic surfactants in our invention.

Typically the cationic surfactant may be any water soluble compoundhaving a positively ionised group, usually comprising a nitrogen atom,and either one or two alkyl groups each having an average of from 8 to22 carbon atoms.

The anionic portion of the cationic surfactant may be any anion whichconfers water solubility, such as formate, acetate, lactate, tartrate,citrate, chloride, nitrate, sulphate or an alkylsulphate ion having upto 4 carbon atoms such as methosulphate. It is preferably not a surfaceactive anion such as a higher alkyl sulphate or organic sulphonate.

Polyfluorinated anionic, nonionic or cationic surfactant may also beuseful in the compositions of our invention. Examples of suchsurfactants are polyfluorinated alkyl sulphates and polyfluorinatedquaternary ammonium compounds.

Compositions our invention may contain a semi-polar surfactant such asan amine oxide, e.g. an amine oxide containing one or two (preferablyone) C₈₋₂₂ alkyl group, the remaining substituent or substituents beingpreferably lower alkyl groups, e.g. C₁₋₄ alkyl groups or benzyl groups.

Particularly preferred for use according to our invention aresurfactants which are effective as wetting agents, typically suchsurfactants are effective at lowering the surface tension between waterand a hydrophobic solid surface. We prefer surfactants which do notstabilise foams to a substantial extent.

Mixtures of two or more of the foregoing surfactants may be used. Inparticular mixtures of non-ionic surfactants with cationic and/oramphoteric and/or semi polar surfactants or with anionic surfactants maybe used. Typically we avoid mixtures of anionic and cationicsurfactants, which are often less mutually compatible.

Preferably the THP and the surfactant are present in a relative weightconcentration of from 1:1000 to 1000:1, more usually 1:50 to 200:1,typically 1:20 to 100:1, most preferably 1:10 to 50:1, e.g. 1:1 to 20:1especially 2:1 to 15:1.

Effective doses of the mixture are typically from 0.5 ppm to 2,000 ppm,more usually 2 ppm to 1,000 ppm, e.g. 5 ppm to 500 ppm especially 10 to250 ppm.

The composition may additionally contain other biocides, waterdispersants, antifoams, solvents, scale inhibitors, corrosioninhibitors, oxygen scavengers and/or flocculants.

Our invention includes aqueous solutions containing a biocidally activeconcentration of a composition of the invention. Such solutions may bewater systems or aqueous based products containing functionalingredients as described in GB 2 145 708. Our invention also includesanhydrous, and concentrated aqueous, formulations adapted to provide theaforesaid products on dilution with water.

Scale or corrosion inhibitors which may be added to the water to betreated in conjunction with the present invention include phosphonates,polymaleates, polyacrylates, polymethacrylates, polyphosphates,phosphate esters, soluble zinc salts, nitrite, sulphite, benzoate,tannin, ligninsulphonates, benzotriazoles and mercaptobenzothiazoles alladded in conventional amounts. The scale and/or corrosion inhibitors maybe added to the water separately from or in association with thephosphonium compound and surfactant. There may be added to the water tobe treated oxygen scavengers, flocculants such as polyacrylamidedispersants, antifoams such as silicones or polyethyleneoxylatcdantifoams or other biocides such as tin compounds or isothiazolones.

The mixture according to our invention may be prepared in situ by addingthe THP, the biopenetrant synergist, and optionally the surfactantseparately to the water system to be treated. Alternatively andpreferably the components may be premixed, either alone, provided thatthey are miscible in the desired proportions, or with water or othersolvents including C₁₋₄ monohydric and polyhydric alcohols, ketones. ordispersants such as polyclectrolytes. Typically THP is miscible withcationic surfactants of the quaternary ammonium and phosphonium type,but mixtures with non-ionic surfactants may require dilution with wateror solvents.

The microorganisms to be treated are usually bacteria, fungi, yeasts,and algae that grow in aquatic environments,. Included in thisclassification are sulphate reducing bacteria, e.g. Desulphovibrio,which may occur in oil installations, iron bacteria, e.g. Gallionellaand slime forming bacteria, e.g. Pseudomonas, which last areparticularly troublesome in aerated aqueous systems.

The water to be treated may be industrial cooling water, e.g. for powerstations or chemical plants or for steel or paper or brewing and may beused in closed circuit or in open circuit involving evaporation incooling towers. Alternatively the water may be process water, especiallyprocess water containing significant sources of nutrients formicroorganisms such as process water for paper making plants andbreweries. Injection water or drilling fluids for oil fields or waterproduced from oil fields or water used in reverse osmosis plants, e.g.to provide industrial processes or boilers feed water, may be treated.

Other aquatic environments which may be treated with the synergisticbiocidal mixtures according to the method for the invention are coolingor process water in board mills. fertiliser manufacture, oil refineries,primary metals manufacture, e.g. steel or copper, petrochemicals, rubbermanufacture, textile and fabric industries, industrial gas manufacture,minerals recover, glass and ceramic manufacture, food industry, leathermanufacture, heavy and light engineering, including metal fabricationand automotive engineering, furniture manufacture, electronics industryand surface coating and adhesives manufacture and other manufacturingindustries.

The process is also applicable to the treatment of geothermal water,water in domestic, industrial and institutional central heating and airconditioning systems and water used for hydrostatic testing of pipelinesand vessels, swimming baths and as cooling water for ships and marineengines.

The invention is also applicable to the control of microbialcontamination in a wide variety of aqueous based products. For examplecompositions of the invention may be added to a variety of solutions andemulsion compositions such as paints, cutting oils, bitumen and taremulsions, adhesives, weedkillers and insecticides, as well as to solidor concentrated compositions for addition to water in the preparation ofsuch products. The invention, therefore, further provides aqueous basedproducts which are subject to microbial spoilage to which has been addeda bacteriostatic or bactericidal quantity of a THP salt, a biopenetrantsynergist as aforesaid and, optionally, a surfactant. Typically suchcompositions consist of aqueous solutions, suspensions or emulsions ofat least one functional ingredient, together with a minor proportion ofa composition of the invention, sufficient to inhibit growth ofmicroorganisms therein.

The systems to which the invention is particularly applicable arc thoseinvolving the circulation or storage of substantial quantities of water,under conditions favouring the multiplication of bacteria, especiallyhardy bacteria such as P Aeruginosa, e.g. conditions involvingmaintaining or periodically raising the water to super ambienttemperatures favouring bacterial proliferation, or maintaining nutrientsfor the bacteria in the water systems.

The invention will be illustrated by the following examples:

EXAMPLE 1

THPS/WSCP mixture was compared with two commercial THP/anionicsurfactant products for control of legionella pneumophila.

METHODOLOGY Parameter Details Test medium Sterile WHO Standard hardnesswater (total hardness 342 mg liter⁻¹) plus 3 mg liter⁻¹ iron as ferricsulphate Biocides Stock solutions 10 × the concentration to be testedAre prepared in WHO standard hardness water pH 8.0 ± 0.2 pH adjusterBoric acid/borax buffer as contained in the test Medium Test organism L.pneumophila sg 1 (NCTC 11192) Test volume 10 ml Contact temp 21 ± 1° C.Contact times 0, 3, 4 and 6 hours Inoculum level To give an initialconcentration of approximately 1 × 10⁵ cfu/liter Preparation ofResuscitate test organism from lyophilised culture. inoculum Prepare 48h plate culture on BCYE agar. Hold at 4° C. overnight. Suspend in 10 mlof test medium. Test method Add 1 ml of biocide stock solution to 8 mlof test Medium. Control contains 9 ml of test medium only. At time 0 hadd 1 ml of inoculum. After the Appropriate contact times remove 1 mland make serial 10 × dilutions. Enumeration By performing Miles andMisra dilution counts method onto BCYE agar plates. Replication Spot 33microliters of each dilution in triplicate onto dry BCYE agar plates toobtain a mean count of surviving legionellae. Plate 37 ± 1° C.incubation temperature Plate 7 days incubation period Expression Givenumber of control and surviving legionellae and of results the log 10reduction in numbers of biocide-treated cell suspensions compare to theappropriate controls.

RESULTS The results are summarised below 3 Hour Contact time 4 HourContact Time 6 Hour Contact Time Product 25 ppm 50 ppm 100 ppm 25 ppm 50ppm 100 ppm 25 ppm 50 ppm 100 ppm 34% THP 2% anionic surfactant 1 × 10²6 × 10² 1.6 × 10³ 1.5 × 10² 15 ND 30   ND ND (Comparison A) 74% THP 1%anionic surfactant 6 × 10⁴ 4.5 × 10²   ND 1.4 × 10⁴ 6 × 10² ND 4.5 × 10²ND ND (Comparison B) 50% active THP/0.7% WSCP (Example) 3 × 10³ ND ND5.3 × 10² ND ND 30.00 ND ND Notes: i) ND - Non Detected ii) The controlwas 1 × 10⁵ iii) The following conclusions apply:- A - Good activitywithin 4 hours at 50 ppm or above B - Good activity within 3 hours at100 ppm or 6 hours at 50 ppm Example - Good activity within 3 hours at50 ppm or above

The example of the invention also showed superior performance toconventional THP surfactant formulations, to WSCP alone and to THP alonein reducing planktonic bacteria.

The example gave less than half the foaming observed using surfactantcontaining formulations.

EXAMPLE 2

An aqueous solution comprising 50% THPS and 2% WSCP was added toalginate beads infected with sulphate reducing bacteria When dosed at250 ppm, solution gave a 100 fold reduction in bacterial counts,compared with a control, after two weeks incubation.

At 500 ppm the solution gave a total kill.

EXAMPLE 3

An aqueous solution comprising 500% THPS and 2% methyl carbitol(diethylene glycol monomethyl ether) was added to alginate beadsinfected with sulphate reducing bacteria When dosed at 250 ppm, thesolution gave a 100 fold reduction in bacterial counts, compared with acontrol, after two weeks incubation. A mixture of 50% THP and 2%cationic surfactant was inactive at this concentration. At 500 ppm thesolution gave a total kill.

The example of the invention also showed superior performance toconventional THP surfactant formulations, to methyl carbitol and to THPalone in controlling both sulphate reducing and planktonic aerobicbacteria.

The example gave less than half the foaming observed using surfactantcontaining formulations.

The mixture also gives effective control over fungi and algae.

EXAMPLE 4

The alginate bead test of examples 2 and 3 was repeated using sodiumnaphthalene sulphonatelformaldehyde condensate as the synergist. As 250ppm the solution gave a 100 fold reduction in bacterial counts after twoweeks incubation. At 500 ppm the solution gave a total kill. The volumeof foam generated when air was bubbled through the system containing 750ppm of the active biocidal mixture was half that using THP alone.

EXAMPLE 5

The alginate bead test of Example I was repeated using generalheterotroph bacteria and a residence time of two hours. For comparisonwe used the most commonly used commercial THP biocide product which isan aqueous solution comprising 50% THPS and 2% of an anionic surfactantavailable commercially under the Registered Trade Mark “DOWFAX” 2A1.

Various mixtures each comprising 50% THPS and 2% of biopenetrant werecompared at 250 ppm and at 125 ppm dosage. The log reduction inbacterial counts is given in the table.

TABLE LOG BIOPENETRANT FUNCTIONALITY REDUCTION Comparative Surfactant250 ppm 3.7 125 ppm 3.0 Sodium xylene sulphonate Hydrotrope 250 ppm 4.7125 ppm 2.7 THP a condensate “Syntan” 250 ppm 5.00 125 ppm 3.70Formaldehyde/dihydroxy- “Syntan” phenylsulphono poly condensate 250 ppm4.0 125 ppm 2.7 Urea 250 ppm Hydrotrope 6.7 125 ppm 4.0

In each case the biopenetrant of the invention showed improved biocidalactivity compared with the surfactant in the comparative example, andgave substantially less foaming.

EXAMPLE 6

The comparative formulation of Example 5 was compared with a mixture of50% THPS, 1% surfactant and 1% diethylene glycol monomethyl ether. Themixture gave greater log reductions than either the comparativeformulation or the formulation of Example 3.

What is claimed is:
 1. A biocidally synergistic mixture comprising THPand at least one THP-compatible non-surfactant biopenetrant wherein saidbiopenetrant is a polymer or copolymer, having a plurality of quaternaryammonium groups, and the concentration of THP is from 10 to 75% byweight and the concentration of biopenetrant is from 0.1 to 10% byweight.
 2. A composition according to claim 1 wherein said biopenetrantis a compound having a polymeric cation with a formula

wherein each R is a divalent organic group constituting, with theammonium group, a monomeric residue, or is separately selected from twoor more comonomeric residues and each R¹ is an alkyl or hydroxyalkylgroup, X is hydrogen or a monovalent inorganic or organic end cappingunit and n is from 2 to
 3000. 3. A composition according to claim 1consisting of an aqueous solution wherein the concentration of THP isfrom 30 to 50% by weight of the solution and the concentration ofnon-surfactant biopenetrant synergist is from 0.5 to 2% by weight of thesolution.
 4. A composition according to claim 1 additionally comprisinga surfactant.
 5. A composition according to claim 4 wherein thesurfactant is present in a weight proportion of from 50:1 to 1:200 basedon the weight of the THP.
 6. A method for treating aqueous systems toinhibit or destroy microbial contamination, which comprises addingthereto, together or separately, a biocidally synergistic amount of THP,at least one THP-compatible non-surfactant biopenetrant and, optionally,a surfactant, wherein said biopenetrant comprises a polymer orcopolymer, having a plurality of quaternary ammonium groups and theconcentration of THP is from 10 to 75% by weight and the concentrationof biopenetrant is from 0.1 to 10% by weight.